The present invention relates to a DC/DC charge and power supply converting module, and more particularly to an integrated converter which can be used as a regulated power supply and a DC/DC charger.
It is well known that all electric appliances are operated under either one or both of two kinds of power supply, the DC (direct current) supply and the AC (alternating current) supply. For some small household appliances, such as a mobile phone and a digital camera, direct current is used as the power by utilizing a rechargeable battery. In order to charge the battery when its capacity is used up, two kinds of chargers, the AC/DC charger and the DC/DC charger, can be used. Since the AC/DC charger only can be used in-house as it must be associated with an AC supply, the DC/DC charger is more useful as its use is not restricted in the way of the AC/DC charger. On the other hand, most of the small electrical appliances are supplied with power by a relatively low voltage. To operate the small electrical appliances, a DC/DC converter is required for converting a high voltage to such a low voltage.
To meet the above needs, various DC/DC converters have been developed. However, conventional DC/DC converters have several disadvantages. First, a conventional DC/DC converter generally comprises a number of parts and elements so that a large circuit board is necessary for combining these elements, thereby resulting in a relative large volume of the converter. To solve this problem, the DC/DC converter has to be separated from and electrically connected with the electrical appliance, as an independent module. Secondly, as mentioned above, the construction of the DC/DC converter is relatively complicated. Therefore, it is hard to improve efficiency during the production process of the converter. Furthermore, a conventional DC/DC converter can output only a single voltage. Therefore, it can not meet the demands of multiple voltages in actual use. Although certain types of DC/DC converters have been developed which are able to output multiple voltages, they are still found unsatisfactory in operation because switching between the multiple voltages is accomplished by addition of a plurality of switches. Obviously, the structure of the converter becomes more complicated.
The main object of the present invention is to provide a DC/DC charge and supply converting module which has a function of constant-current charging an electrical appliance.
A second object of the present invention is to provide a DC/DC charge and supply converting module which has a function of supplying constant-voltage power to an electrical appliance.
In accordance with one aspect of the present invention, the DC/DC charge and supply converting module comprises a DC/DC converter and a charge module connected with a control end and an output end of the DC/DC converter. The charge module includes a comparator having an output end connected to the control end of the DC/DC converter, a constant current source having an input end acting as a measuring end for measuring a voltage across a rechargeable battery, and an output end connected to a first input end of the comparator, a bleeder circuit having an input end acting as a feedback signal end, and an output end connected to a second input end of the comparator.
In accordance with another aspect of the present invention, the DC/DC converter comprises two driving transistors respectively connected between an input supply and an output end thereof for controlling an output voltage, a latch circuit composed of an RS inverter and having an output connected to a base electrode of one of the driving transistors, an AND gate having an output end connected to an input end S of the latch circuit, a surge wave absorber having an input end connected with the input supply and an output end connected with a first input end of the AND gate and an input end R of the latch circuit; and a comparator having an output end connected to a second input end of the AND gate, a negative input end being supplied with a reference voltage by the charge module, and a positive input end connected with the charge module and acting as a control end, and a reference voltage generator for supplying a reference voltage to the surge wave absorber.
In accordance with a further aspect of the present invention, the constant current source is composed of a first and a second transistor, and a bleeder circuit used for measuring a charge voltage. The bleeder circuit includes a first and a second divider resistor, an input end of the bleeder circuit being used as a measuring end (FDBK) connected to a battery of an electrical appliance for measuring a battery voltage, a base and a collecting electrode of the first transistor being interconnected and coupled to a negative input end of the comparator and an output end of the bleeder circuit, a base and a collecting electrode of the second transistor being interconnected and coupled with an emitting electrode of the first transistor via a resistor, an emitting electrode of the second transistor being connected with the base electrode of the first transistor and the negative input end of the comparator.